Organolithium compounds play an important role in preparative organic chemistry when lithium or an organic substituent is to be incorporated in an organic compound.
The organolithium compounds are usually susceptible to reaction with air and moisture and, for this reason, may be handled only with precautions. For instance, butyllithium is a self-igniting liquid, which is susceptible to hydrolysis. For this reason, butyllithium is usually handled in 15 to 25% solutions, e.g. in alkanes, or in about 30% suspensions of paraffins (Rompp Chemie Lexikon, 8th edition, 1979, page 547). By contrast with their higher homologs, methyllithium and ethyllithium are insoluble or hardly soluble in saturated and in saturated hydrocarbons and as solids are highly pyrophoric so that they can be handled only with difficulty.
From Published German application No. 36 37 780, it is known that the disadvantages of solutions of organomagnesium and organolithium compounds can be avoided by using them in pulverulent mixtures of clay dust and solutions of organomagnesium or organolithium compounds.
While the powders thus obtained are less susceptible to hydrolysis, they are pyrophoric, particularly with the organolithium compound.
In order to reduce their pyrophoric character, undesirably high clay contents are required, which in organic syntheses act as undesired accompanying substances and as sorbents.
In safety regulations for handling butyllithium, it has been stated that material which is flowing out can be treated with pulverulent limestone for preventing a fire. From "Synthesis" (1983), page 387, it is known to modify complex inorganic hydrides by incorporating them in silica gel or alumina.
The synthesis of methyllithium or ethyllithium is effected in a known manner, namely, methyllithium contained in diethyl ether or tetrahydrofuran and ethyllithium contained in hexane, by the reaction of lithium metal and alkyl halide in accordance with the formula: EQU R Hal+2Li.fwdarw.R Li+Li Hal
Lithiummethyl has the highest solubility in diethyl ether, in which it has a solubility of about 5%. Solutions of ethyllithium have an ethyllithium concentration of about 2%. But the restriction to diethyl ether restricts the use of that compound, because numerous users hesitate to use diethyl ether on an industrial scale owing to its high vapor pressure and the formation of peroxide upon evaporation and try to avoid such use, if possible. In addition, the solutions have only relatively low concentrations.